DESCRIPTION: (Adapted from the applicant' abstract). The applicants propose to develop an implantable pressure sensor made from single crystal silicon. The approximately 1-mm diameter x 2.5-mm long sensor will obtain its performance from white light interferometry to make a precision, noncontact measurement of diaphragm displacement. Particular design features make it insensitive to light intensity losses. Mechanically, the sensor element is configured for easy insertion, high biocompatibility, and long term performance in the biological environment. The sensor will be attached to an equally durable and biocompatible cable of 1-mm diameter, essentially equivalent to a pacemaker wire in construction with the addition of a 0.1-mm optical fiber to the wire bundle. The Phase I specific aim is to design the sensor sections and demonstrates its accuracy and stability under in-vitro conditions. Prototype cable and external electronics will be used for testing. The goal and the criteria for success of Phase I is for 0.05 mmHg accuracy and 0.1 mmHg /24 hr drift. Phase II will complete the development and in-vivo demonstration of the total system. PROPOSED COMMERCIAL APPLICATION: Medical research, diagnosis, patient treatment and implantable device aspects of the biomedical industry would benefit significantly from the proposed fiber-optic pressure sensor. The development of this sensor has the potential to fulfill important needs in ambulatory monitoring of blood pressure, circulatory support systems, diagnostic instrumentation for small animals and early detection of heart failure. The aerospace industry could also significantly benefit from this sensor device especially for engine control as well as wind tunnel applications. Process industries such as the petrochemical industry could benefit significantly from a drift-free fiber-optic pressure sensor.